$re = '/key\": \"material\",.*?\"value\": \"(.*?)\",/s';
$str = '{
"key": "width",
"value": "1200",
"label": "Width (mm)",
"choice": ""
},
{
"key": "height",
"value": "900",
"label": "Height (mm)",
"choice": ""
},
{
"key": "material",
"value": "paper",
"label": "Material",
"choice": "Paper"
}]';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php